Hi, new user just dipping into dynamo, I have been looking at the samples that came with the install and also some online resources.
However I’ve run into an issue that when I create a script and save it, then close and reopen the file, some of the nodes and connectors have disappeared.
Can anyone shed any light on what is happening?

Some fixes on civil 3d side has been done but it will not be available until 2020 update1. So if you want to use it earlier, you can get the AeccHydroCalcsMgd.dll file from the 2020 update 1 beta2 installer (whichever way that you can get it).
Also cc @andre.sprong